Stock Split Calculator

The short answer: your total value stays the same. A stock split changes two things — the number of shares you own and the price per share — but they move in opposite directions so the product (total value) is unchanged.

The math:

• New Shares = Old Shares × (Split Numerator / Split Denominator)
• New Price = Old Price × (Split Denominator / Split Numerator)
• Total Value = Old Shares × Old Price = New Shares × New Price (always equal)

Example with a 4:1 split: You own 50 shares at $800 each ($40,000 total). After the split, you own 200 shares at $200 each ($40,000 total). Nothing changed except the label on each piece.

What does change after a split:

• Cost basis per share — Your broker automatically adjusts your cost basis. If you bought at $400 pre-split and there's a 4:1 split, your new cost basis is $100 per share. This matters for tax calculations when you eventually sell.
• Options contracts — Existing options are adjusted. A call option for 100 shares at a $800 strike becomes an option for 400 shares at a $200 strike. The total value of the contract stays the same.
• Per-share metrics — Earnings per share (EPS), dividends per share, and book value per share all get divided by the split ratio. This is purely mathematical and doesn't represent any change in the company's profitability.

One common misconception is that splits make you "richer." They do not. If a stock rises after a split, it's because of market forces and investor sentiment — not because of the split itself.

A reverse stock split is the opposite of a forward split. Instead of receiving more shares at a lower price, your shares are consolidated into fewer shares at a higher price. For example, in a 1-for-10 (1:10) reverse split, every 10 shares you own become 1 share worth 10 times the previous price.

Like forward splits, reverse splits do not change the total value of your position. If you owned 1,000 shares at $2 ($2,000 total), a 1:10 reverse split gives you 100 shares at $20 ($2,000 total).

Why companies do reverse splits:

• Exchange compliance — Major exchanges like the NYSE and Nasdaq have minimum price requirements (typically $1). If a stock trades below $1 for too long, it risks being delisted. A reverse split boosts the price above the threshold.
• Institutional appeal — Many institutional investors and mutual funds have policies against buying stocks below $5 or $10. A reverse split moves the share price into an "acceptable" range for these buyers.
• Reducing share count — Companies with billions of shares outstanding may reverse split to bring the share count to a more conventional number.

Is it a red flag? Often, yes — but not always. Here's the nuance:

• Concerning signal — Most reverse splits happen because the stock price has fallen dramatically. Statistically, stocks that do reverse splits tend to underperform in the following 12 months. The reverse split doesn't fix the underlying business problems that caused the decline.
• Not always bad — Some healthy companies do reverse splits for strategic reasons (e.g., to reduce share count after a spinoff or restructuring). Citigroup did a 1:10 reverse split in 2011 after the financial crisis, and the stock has performed reasonably well since.

The key question isn't whether a reverse split happened — it's why. Dig into the company's financials, revenue trajectory, and management commentary to understand whether the underlying business is improving or deteriorating.

Yes, stock splits affect all of these — but in a way that preserves the total economic value. Everything gets adjusted proportionally so you're neither better nor worse off.

Options contracts:

• The Options Clearing Corporation (OCC) automatically adjusts existing contracts when a split occurs. In a 2:1 split, one contract for 100 shares at a $200 strike becomes one contract for 200 shares at a $100 strike.
• For "whole" splits (2:1, 3:1, 4:1), each original contract is split into multiple standard 100-share contracts. For non-standard splits (3:2, 5:4), you may end up with non-standard contracts that cover odd share amounts. These "adjusted" options can have lower liquidity.
• The total value of your option position is the same immediately after the split. However, if you're trading options, post-split contracts may have better liquidity due to the lower per-share price attracting more participants.

Dividends:

• The per-share dividend is adjusted proportionally. If a company paid $2 per share and does a 2:1 split, the new dividend is $1 per share. You receive the same total dollar amount because you own twice as many shares.
• Companies sometimes use a split as an opportunity to increase the dividend, but this is a separate decision from the split itself. Don't assume a split means a dividend increase.

Cost basis:

• Your broker automatically adjusts your per-share cost basis. Bought at $800 pre-split with a 4:1 split? Your new cost basis is $200 per share. This is critical for accurate tax reporting when you sell.
• If you purchased shares in multiple lots at different prices, each lot's cost basis is adjusted individually. Your overall gain or loss when selling remains exactly the same.
• Important: Some international brokers may not automatically adjust cost basis for splits of foreign stocks. Always verify your records, especially for non-US holdings.

Some of the biggest names in the market have split their stock multiple times over the decades. These examples show how splits are a routine corporate action for growing companies, not a cause for alarm.

Notable stock splits:

• Apple (AAPL) — Has split five times in its history. The most recent was a 4:1 split in August 2020, bringing the price from roughly $500 to $125. If you bought one share at Apple's 1980 IPO price and held through all splits, that single share would have become 224 shares.
• Tesla (TSLA) — Completed a 5:1 split in August 2020 when shares were trading around $2,200, followed by a 3:1 split in August 2022. The splits were partly credited with making TSLA more accessible to retail investors.
• Amazon (AMZN) — After three splits in the late 1990s, Amazon went over 20 years without splitting. It finally did a 20:1 split in June 2022 when the stock was trading near $2,800, bringing the price to around $140.
• NVIDIA (NVDA) — Completed a 10:1 split in June 2024 as its stock surged past $1,200 on AI demand. This brought the price to around $120 and made it more accessible to retail investors.
• Berkshire Hathaway (BRK.A) — Warren Buffett famously never split the Class A shares, which trade above $600,000 per share. His reasoning: he wants long-term investors, not speculators. He did create Class B shares (BRK.B) at 1/1,500th the price as an alternative.

Famous reverse splits:

• General Electric (GE) — Did a 1:8 reverse split in 2021 as part of its restructuring effort to return to a more "normal" share price after years of decline.
• Citigroup (C) — Executed a 1:10 reverse split in 2011 after the financial crisis had pushed shares into the low single digits.

Historically, companies that split tend to outperform in the short term after the announcement — not because of the split itself, but because splits typically happen after a period of strong price appreciation that reflects solid business performance.

From a pure valuation standpoint, it makes no difference. A stock split does not change the intrinsic value of the company. Buying 1 share at $800 before a 4:1 split gives you the same position as buying 4 shares at $200 after the split. Your total investment and your percentage ownership in the company are identical.

Arguments for buying before a split:

• Pre-split momentum — Split announcements often generate positive sentiment and media coverage. Some traders try to capture this momentum by buying between the announcement date and the split date. Research shows a modest average price bump in this window, though it's far from guaranteed.
• Options positioning — If you plan to sell covered calls, having round lots (multiples of 100 shares) matters. Buying before the split at a higher price per share means you need fewer dollars to establish a round lot.

Arguments for buying after a split:

• Lower per-share price — Even with fractional shares available, some investors prefer owning whole shares. A post-split price may fit better within a fixed monthly investment budget.
• Avoid pre-split hype — Split announcements sometimes create temporary overvaluation. Waiting for the dust to settle can mean buying at a more rational price.
• Better liquidity — Post-split trading volume is usually higher, which means tighter spreads and better execution on your order.

The bottom line: focus on valuation, not the split. Whether a stock is worth buying depends on its fundamentals, growth prospects, and current price relative to intrinsic value — not on whether a split is happening. A DCF model is the right tool for answering that question.

When comparing a stock's current price to its historical price, you need to account for all splits that have occurred in between. Otherwise, you'll get misleading numbers. For example, Apple's IPO price was $22 in 1980, but after multiple splits, the split-adjusted IPO price is well under $1.

The formula for split-adjusted historical price:

Adjusted Price = Historical Price / Cumulative Split Factor

The cumulative split factor is the product of all split ratios between the historical date and today. For example, if a stock had a 2:1 split in 2015 and a 4:1 split in 2020, the cumulative factor is 2 × 4 = 8.

Step-by-step example:

• You bought a stock at $400 in 2018.
• There was a 2:1 split in 2020 and a 5:1 split in 2023.
• Cumulative factor = 2 × 5 = 10.
• Split-adjusted purchase price = $400 / 10 = $40.
• If the stock trades at $60 today, your actual gain is from $40 to $60 (50%), not from $400 to $60 (which would incorrectly suggest an 85% loss).

Practical tips:

• Use financial data providers — Sites like Yahoo Finance and Google Finance automatically display split-adjusted historical prices. When you look at a 5-year chart, the prices shown have already been adjusted for all splits. This is the easiest approach for most investors.
• Check your brokerage statements — Your broker adjusts cost basis automatically, but it's worth verifying, especially for older positions or international stocks where automatic adjustments may not be reliable.
• Reverse splits matter too — A 1:10 reverse split means you divide the historical price by 0.1 (or equivalently, multiply by 10). Always include reverse splits in your cumulative factor calculation.

Getting split adjustments right is essential for accurate performance tracking. If you're comparing returns across multiple stocks, make sure all prices are on a split-adjusted basis — otherwise, you're comparing apples to oranges.